A U.S. Marine with 1st Battalion, 6th Marine Regiment,

A U.S. Marine with 1st Battalion, 6th Marine Regiment, 2nd Marine Division (MARDIV), shares a laugh with a fellow Marine before beginning their decent from landing zone quail down to lower base camp, after a day of pre-environmental training classes, where they learned the fundamentals of mountain warfare and survival, prior to the start of Mountain Exercise 5-15 at the Marine Corps Mountain Warfare Training Center, Bridgeport, Calif., Sept. 6, 2015. Marines participate in a month-long field exercise focusing on core mission essential tasks such as assault climbing, animal packing and small unit movements, to strengthen expeditionary high altitude warfare tactics in a mountainous environment against a hybrid threat, as they prepare for world-wide deployment. (U.S. Marine Corps photo by Cpl. Kelly L. Street, 2D MARDIV COMCAM/Released)